The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A093121 A Jacobsthal Fibonacci product. 1
 1, 0, 4, 6, 30, 80, 286, 882, 2924, 9350, 30438, 98208, 318278, 1029210, 3331820, 10780014, 34888062, 112894960, 365344142, 1182264930, 3825911596, 12380874550, 40065409014, 129654294336, 419570260150, 1357757640330 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS Form a graph from a triangle and its midpoint triangle. A093121 counts closed walks of length n at a vertex of the midpoint triangle in this configuration. LINKS Table of n, a(n) for n=0..25. Index entries for linear recurrences with constant coefficients, signature (1,7,2,-4). FORMULA G.f.: (1-x-3x^2)/((1+x-x^2)(1-2x-4x^2)); a(n)=A078008(n)*A000045(n+1); a(n)=(2^n/3+2(-1)^n/3)(((1+sqrt(5))/2)^(n+1)/sqrt(5)-((1-sqrt(5))/2)^(n+1)/sqrt(5)). MATHEMATICA LinearRecurrence[{1, 7, 2, -4}, {1, 0, 4, 6}, 30] (* Harvey P. Dale, Aug 26 2019 *) CROSSREFS Sequence in context: A046849 A090530 A154667 * A248048 A209298 A075590 Adjacent sequences: A093118 A093119 A093120 * A093122 A093123 A093124 KEYWORD easy,nonn AUTHOR Paul Barry, Mar 22 2004 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified February 29 10:50 EST 2024. Contains 370425 sequences. (Running on oeis4.)